PROTOLITH RECOVERING AND PALEOSEDIMENTARY ENVIRONMENT OF LAOLING GROUP IN SOUTHERN JILIN PROVINCE

Laoling group in Southern Jilin Province can be divided into lower subgroup (including Dadongcha formation, Linjiang formation and Dalizi Formation) and upper subgroup (includint Shiqinggou and Zhenzhumen formations). The main protolith types of Laoling group are mudstone, sandstone, siltstone, silty claystone, pelitopsammite, quartz sandstone, dolomitic claystone and apogrit, which were formed in sedimentary environment. The paleosedimentary environment experienced high energy offshore facies during Linjiang formation, low energy neritic facies, neritic-continental shelf facies, semi-closed lagoon facies and high energy sand flat facies in Dalizi formation, high energy offshore facies and slow energy semi-closed platform facies in Shiqinggou formation, low energy semi-closed platform facies, open platform facies, high energy platform margin facies, and low energy neritic-continental shelf facies in Zhenzhumen formation. The analysis shows that the change of paleosedimentary environment was corresponding with that of the eustatic sea level.